It cannot have escaped any drivers notice that the severe winter has caused sudden deterioration in road surfaces. The concrete section of the M90 was no exception where the fast lane was under traffic management for some weeks due to the micro surfacing¬† not being there any more. The micro surfacing (slurry sealing?) was a complete success as I watched it being applied with some wonderment, it did give a smoother and quieter ride, and the joints from slab to slab did not cause cracks, what was that wonder material?¬† I don't know. However the repairs to these extensive areas have been done with a thin surfacing, a modified SMA, I did enquire from Ennstone who manufactured and laid it what was in it to resist the joint in the concrete pavement not reflecting through the new SMA. Kind of got the brochure answer, much modified and very expensive, but I know SBS, a liquid rubber binder was in there. I have delayed putting up this post as I wanted to see the if it worked for a few months, it has.
Well done the techys at Ennstone, if this lasts for a year, through minimum and maximum expansion and contraction, then you have the solution to resurface this whole concrete section of carriageway, that has been of tremendous value to us the tax payers, but needs resurfacing. Hence the micro resurfacing section that was done but in part the weather claimed.
I have to point out when working for Wimpey Asphalt in Hong Kong in the 90s we devised (before I arrived) a mix to replace joints on bridge approaches, the annual pavement temperature range in Hong Kong is considerable, I will guess it at 20 degrees C, but these asphaltic plug joints showed no cracking where the line markings over them did. I recall 3 litres a tonne of SBS as an additive on its own with straight run 50 pen bitumen being added.
This is what happens when engineers and asphalt technologists ignore the specification for highway works, or any other imposed spec, and come up with a solution presumably backed by PI to give client comfort. It is now acknowledged that we imported a surfacing material called SMA and modified it to give a surface texture identical with the HRA WC it replaced. This was the government doing technology, must have skid resistance which equals a macro texture of 1.5mm, it hasn't worked, particularly on roundabouts, stressed sites and where laying conditions are compromised. If you get rid of the thick binder coating on the surface on SMAs after laying, the skid resistance is adequate with 1.0mm texture giving a much enhanced durable to fretting mix. (exactly what the Germans do from whom we copied it and modified it to make it "frettable") This has only taken ten years for the trunk road responsible agents to learn.
Dear Transport Scotland you never have followed the HA, now you're taking a step forward on the M90 by letting the industry provide the technical solution. Globally this isn't new, but here a welcome change.